The social brain meets neuroimaging

Recent neuroimaging studies in humans have indicated that individual differences in social network size correlate with amygdala volume and the volume of brain regions associated with theory of mind. A new article demonstrates that this is also true for monkeys. Taken together, these findings provide crucial support for the social brain hypothesis.     

Developmental structure in brain evolution

How does evolution grow bigger brains? It has been widely assumed that growth of individual structures and functional systems in response to niche-specific cognitive challenges is the most plausible mechanism for brain expansion in mammals. Comparison of multiple regressions on allometric data for 131 mammalian species, however, suggests that for 9 of 11 brain structures taxonomic and body size factors are less important than covariance of these major structures with each other. Which structure grows biggest is largely predicted by a conserved order of neurogenesis that can be derived from the basic axial structure of the developing brain. This conserved order of neurogenesis predicts the relative scaling not only of gross brain regions like the isocortex or mesencephalon, but also the level of detail of individual thalamic nuclei. Special selection of particular areas for specific functions does occur, but it is a minor factor compared to the large-scale covariance of the whole brain. The idea that enlarged isocortex could be a "spandrel," a by-product of structural constraints later adapted for various behaviors, contrasts with approaches to selection of particular brain regions for cognitively advanced uses, as is commonly assumed in the case of hominid brain evolution.     

Do big-brained animals play more? Comparative analyses of play and relative brain size in mammals

It has been hypothesized that play is more likely to be present in larger brained species. We tested this hypothesis in mammals using independent contrasts, a method that controls for phylogenetic relatedness. Comparisons across 15 orders revealed that the prevalence and complexity of play was significantly correlated with brain size, with larger brained orders having more playful species. Three orders, Rodentia, Marsupialia, and Primates, were used for within-order comparisons among species and, where possible, among families. The comparisons were not significant for rodents or primates, and those for marsupials yielded inconsistent results. Therefore, although a strong relationship is present at the highest taxonomic level of comparison, it diminishes or evaporates at lower level comparisons.     

Race, brain size, and intelligence: another reply to Cernovsky

Five sets of observations require explanation. Firstly, within both black and white populations there is a small positive correlation between IQ and brain size whether or not there is control for body size. Secondly, racial differences in average brain size occur such that Mongoloids greater than Caucasoids greater than Negroids especially with control for body size. Thirdly, mammals with larger brains relative to their bodies perform better on learning tasks than mammals with smaller brains relative to their bodies. Fourthly, average racial differences on measures of cognitive performance parallel the differences in average brain size. Fifthly, average racial differences on numerous other traits parallel the differences in intelligence and brain size. It is incumbent on scientists to explain these facts.     

Sex differences in human brain size and the general meaning of differences in brain size.

Contrary to commonly held convictions, there is no clear association between brain size and body parameters in humans. Within sexes, once age and health status are controlled for, there is no significant association between brain size and body height for females. For males, body height accounts for no more than .04% of the variance in brain size. The relation between brain weight and body weight is even less clearly defined. Nevertheless, there are large and significant differences in brain size between the sexes. If no adequate body parameters can be found that scale to brain size within the sexes, the marked dimorphism between males and females makes it even more difficult to find a common set of parameters that allow evaluation of brain size differences between sexes. Within and across sexes, there is no convincing link between a limited measure of behavioural capacity (IQ) and brain size. This leads to the more general question: Why would one expect such a link, and, if it is not found, what does this mean in the context of general theories of cortical function?     

EVOLUTION OF THE PSYCHENCEPHALON

In evolving to its great size the human brain has retained the distinctive features and chemistry of three kinds of brains that reflect an ancestral relationship to reptiles, early mammals, and late mammals. It constitutes, so to speak, a psychencephalon comprised of three-brains-in-one, a triune brain. In the evolution from reptiles to mammals two key changes were the development of nursing and maternal care. Through the agency of “newer” parts of the brain a parental concern for family eventually generalizes not only to other members of the species but to the entire biosphere, a psychological development that amounts to the evolution of responsibility and what we call conscience. Given our freedom to decide “yes” or “no” on various issues, we need not look beyond the evolving family to find a reason for being, an ethic to live by.     

Is the social brain theory applicable to human individual differences? Relationship between sociability personality dimension and brain size

Our study intends to examine whether the social brain theory is applicable to human individual differences. According to the social brain theory primates have larger brains as it could be expected from their body sizes due to the adaptation to a more complex social life. Regarding humans there were few studies about the relationship between theory of mind and frontal and temporal brain lobes. We hypothesized that these brain lobes, as well as the whole cerebrum and neocortex are in connection with the Sociability personality dimension that is associated with individuals' social lives. Our findings support this hypothesis as Sociability correlated positively with the examined brain structures if we control the effects of body size differences and age. These results suggest that the social brain theory can be extended to human interindividual differences and they have some implications to personality psychology too.     

What neuroimaging and brain localization can do, cannot do and should not do for social psychology

Interest in bridging social psychology and neuroscience has seen a significant upsurge. Much of this interest has centered on brain localization--the attempt to relate psychological events to locations of brain events. Although many articles have sought to localize brain activity that supports social behavior, scant attention has been paid to the specific methods to be used in integrating brain localization data into psychological theory. The authors describe 4 strategies psychologists can use to integrate brain localization data and psychological theory, and they consider whether social psychology presents special considerations in the use of these strategies. They conclude that brain localization offers a useful tool for some but not all problems in social psychology, and they discuss the types of problems for which it may and may not prove useful.     

Re-evaluating the extractive foraging hypothesis

In his seminal 1992 paper, Dunbar examined three hypotheses advanced to explain primate intelligence, arguing that whereas his social group size hypothesis was supported, neither of two ecological hypotheses, the extractive foraging and frugivory hypotheses, were supported. Following this, and Dunbar's subsequently elaborated argument, many investigators concluded that primate intelligence arose as social rather than ecological adaptations. This paper questions Dunbar's characterization of extractive foraging and social intelligence as alternative hypotheses, raises sampling issues about Dunbar's brain data, species choice, and measurement of extractive foraging. It summarizes the extractive foraging hypothesis, and counters its critics. It reexamines the hypothesis in light of recent behavioral and brain data, new methodology for quantifying extractive foraging, and a new phylogeny of primate intelligence. It concludes that the extractive foraging hypothesis is now supported by several converging lines of evidence.     

Psychosis and autism as diametrical disorders of the social brain

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions.     

Are high-IQ individuals deficient in common sense? A critical examination of the ‘clever sillies’ hypothesis

A controversial hypothesis [Charlton (2009). Clever sillies: Why high-IQ people tend to be deficient in common sense. Medical Hypotheses, 73, 867–870] has recently been proposed to account for why individuals of high-IQ and high social status tend to hold counter-intuitive views on social phenomena. It is claimed that these ‘clever sillies’ use their high general intelligence and Openness to Experience to overanalyze social problems for which socially intelligent/common sense responses would seemingly be more appropriate. The first three sections of this review will consider i) the relationship between general and social intelligence; ii) the role of situational effects on the direction of the correlation between IQ and political attitudes; iii) the behavioral ecology of competitive altruism. While there is no hard evidence for Charlton's hypothesis, sophisticated although ultimately non-rational subjective analyses of social phenomena (i.e. ones that are disconfirmed by data, or reject empiricism) do seem to be favored by individuals in certain high-IQ knowledge work sectors. It is suggested that these function as costly signals of altruism, and that their popularity can best be understood in light of the theory that social attitudes are fundamentally influenced by perceptions of dominance and counter-dominance, with the latter playing an especially significant role in influencing the values systems of contemporary societies where the degree of conspicuous inequality is significantly evolutionarily novel.     

The brain basis of emotion: a meta-analytic review

Researchers have wondered how the brain creates emotions since the early days of psychological science. With a surge of studies in affective neuroscience in recent decades, scientists are poised to answer this question. In this target article, we present a meta-analytic summary of the neuroimaging literature on human emotion. We compare the locationist approach (i.e., the hypothesis that discrete emotion categories consistently and specifically correspond to distinct brain regions) with the psychological constructionist approach (i.e., the hypothesis that discrete emotion categories are constructed of more general brain networks not specific to those categories) to better understand the brain basis of emotion. We review both locationist and psychological constructionist hypotheses of brain-emotion correspondence and report meta-analytic findings bearing on these hypotheses. Overall, we found little evidence that discrete emotion categories can be consistently and specifically localized to distinct brain regions. Instead, we found evidence that is consistent with a psychological constructionist approach to the mind: A set of interacting brain regions commonly involved in basic psychological operations of both an emotional and non-emotional nature are active during emotion experience and perception across a range of discrete emotion categories.     

Caching at a distance: a cache protection strategy in Eurasian jays

A fundamental question about the complexity of corvid social cognition is whether behaviours exhibited when caching in front of potential pilferers represent specific attempts to prevent cache loss (cache protection hypothesis) or whether they are by-products of other behaviours (by-product hypothesis). Here, we demonstrate that Eurasian jays preferentially cache at a distance when observed by conspecifics. This preference for a ‘far’ location could be either a by-product of a general preference for caching at that specific location regardless of the risk of cache loss or a by-product of a general preference to be far away from conspecifics due to low intra-species tolerance. Critically, we found that neither by-product account explains the jays’ behaviour: the preference for the ‘far’ location was not shown when caching in private or when eating in front of a conspecific. In line with the cache protection hypothesis we found that jays preferred the distant location only when caching in front of a conspecific. Thus, it seems likely that for Eurasian jays, caching at a distance from an observer is a specific cache protection strategy.     

人格特质及脑功能连接对社交网络的影响

采用网络分析的方法, 本研究从个体受欢迎程度和个体间亲密程度两方面探究了人格特质对社交网络的影响, 并在此基础上进一步探究了个体间大脑静息态功能连接相似性和社交网络的关系。结果发现：(1)高尽责性的个体在需要“值得信任”特质的社交网络中更受欢迎, 高宜人性的个体在需要“共享时光”的社交网络中更受欢迎; (2)在需要“相同兴趣”特质的社交网络中, 个体间人格相似性和社会距离呈显著负相关关系; (3)同样在需要“相同兴趣”特质的社交网络中, 个体间部分功能连接相似性与社会距离呈显著负相关关系, 这些功能连接主要集中在额顶控制网络以及背侧注意网络; 同时, 部分节点功能连接相似性与社会距离呈显著正相关关系, 这些功能连接主要集中在默认网络。研究结果揭示了人格特质对不同社交网络结构的影响, 以及个体间人格特质相似性和静息态脑网络相似性与社会距离的关系。本研究对理解社交网络的结构, 形成规律以及其中的信息传播规律有着重要启示意义。     

Mouse vocal communication system: Are ultrasounds learned or innate?

Mouse ultrasonic vocalizations (USVs) are often used as behavioral readouts of internal states, to measure effects of social and pharmacological manipulations, and for behavioral phenotyping of mouse models for neuropsychiatric and neurodegenerative disorders. However, little is known about the neurobiological mechanisms of rodent USV production. Here we discuss the available data to assess whether male mouse song behavior and the supporting brain circuits resemble those of known vocal non-learning or vocal learning species. Recent neurobiology studies have demonstrated that the mouse USV brain system includes motor cortex and striatal regions, and that the vocal motor cortex sends a direct sparse projection to the brainstem vocal motor nucleus ambiguous, a projection previously thought be unique to humans among mammals. Recent behavioral studies have reported opposing conclusions on mouse vocal plasticity, including vocal ontogeny changes in USVs over early development that might not be explained by innate maturation processes, evidence for and against a role for auditory feedback in developing and maintaining normal mouse USVs, and evidence for and against limited vocal imitation of song pitch. To reconcile these findings, we suggest that the trait of vocal learning may not be dichotomous but encompass a broad spectrum of behavioral and neural traits we call the continuum hypothesis, and that mice possess some of the traits associated with a capacity for limited vocal learning.     

Effects of Prenatal Social Stress on Offspring Development: Pathology or Adaptation?

ABSTRACT— In nonhuman mammals, the social environment in which pregnant females live is critical for their offsprings' brain development, endocrine state, and social and sexual behavior later in life. Social instability during pregnancy generally brings about a behavioral and neuroendocrine masculinization in daughters and a less pronounced expression of male-typical traits in sons. We favor the hypothesis that such behavioral effects of prenatal social stress are not necessarily "pathological" (nonadaptive) consequences of adverse social conditions. Rather, pregnant mothers could be adjusting their offspring to their environment in an adaptive way.     

An evolutionary look at oddity and schizotypy: How the rise of social brain informs clinical practice

A prominent facet of schizotypy is the recurrence of odd cognitions, emotions, and behaviors. This paper aims to present an evolutionary interpretation of oddity as a risk-minimizing and uniqueness-maximizing strategy for facing the complexity of our hyper-affiliative species. I discuss this hypothesis by exploring the intertwined role of social safety and social cognition in preventing or triggering psychopathology. Since schizotypy is reputed to be a polygenic dimension, its underlying genes are likely involved in both adaptive and maladaptive traits. Consequently, the oddity is presented as both an evolutionary trade-off and a possible advantage in the rise of our complex social brain. The clinical implications of conceptualizing schizotypy and supporting those struggling with maladaptive forms of oddity are discussed.     

The effects of familiar size on judgments of size and distance: An interaction of viewing attitude with spatial cues

Two hypotheses about the effects of familiar size on judgments of size and distance, the cue-conflict hypothesis and the viewing-attitude hypothesis, were examined. In Experiment 1, observers estimated the size and distance of familiar targets with apparent or assumptive instructions under three different spatial cue conditions. In Experiment 2, observers performed tasks similar to those of Experiment 1 with no specific instructions. The main results were: (1) Assumptive instructions facilitate the effects of familiar size in both size and distance judgments, but reducing spatial cues does not, and (2) viewing attitude changes from the apparent to the assumptive when available spatial cues are reduced. Thus, it was concluded that the viewing-attitude hypothesis gives a better account of the effects of familiar size, but that the cue-conflict hypothesis cannot be abandoned, because the number of conflicting cues contributes to the formation of viewing attitude.     

BRAIN ROOTS OF THE WILL-TO-POWER

Abstract. The human brain has evolved to its great size while retaining the anatomical and chemical features of three basic formations that reflect an ancestral relationship to reptiles, early mammals, and late mammals. Such considerations must be taken into account in the origin and expression of individual and collective violence, which operationally depend on power and the orchestrated use of power. Aristotle and Friedrich Nietzsche have respectively provided paradigms of a "great-souled man" and a "superman"— both basically ruthless. In neurobehavioral investigations of the triune brain, one finds the basis for the hierarchical development of ruthless power, merciful power, and transcendental power.     

Survival with an asymmetrical brain: advantages and disadvantages of cerebral lateralization

Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an "evolutionarily stable strategy" under "social" pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.